I did the first 2 terminals, what now? there's nowhere to go
Edit: alt-ctrl-shift-M in the combat level should unlock the gallery...it doesn't work for me tough
After 15 minutes of walking around and peeking through walls by aiming down sights and hugging the wall with my right side, I found out where one of the hidden consoles were... It was really close to the beginning after turning left and going up the ladder.
When you reach this room:
Look to the top left and you should see a little spot you can jump into
Once up top, look left and crawl through the passage
Upon reaching the end there should be two ladders, on opposite sides from each other, you have to climb up one and jump to the other one behind you.
After reaching the top, don't go forward, but turn around and look up a bit and you should see a health pick up (I took the health already so you don't see it in the pic below), climb the ledge on the side and jump up, then turn left and follow the path to the last console.
If you go the opposite way from where the health is, there will be a few enemies, and it takes you to a drop which you can fall into which takes you to the area where the elevator is that leads to the "third" console.